The invention relates to a manual dosing device for dosing liquids.
Manual dosing devices are dosing devices for dosing liquids on which a syringe or pipette tip can be releasably held. Syringes have a syringe cylinder with a syringe plunger which can move therein, and an opening connecting the syringe cylinder to the environment for drawing and releasing liquid. The opening is generally arranged in a tip on the floor of the syringe cylinder. Pipette tips are small tubes that generally narrow downward and have a bottom tip opening for drawing and releasing liquid, and a top tip opening to be connected with a displacement device for air. Manual dosing devices are held in one hand by the user while dosing so that the syringe, or pipette tip, held thereon can be aligned with a vessel or another object from which liquid is to be withdrawn or toward which liquid is to be released. The user can control the withdrawal and release of liquids and possibly additional functions with the same hand with which he holds the manual dosing device. Manual dosing devices are in particular used in laboratories for dosing liquids.
Manual dosing devices are designed as air cushion dosing devices and positive displacement dosing devices. Air cushion dosing devices have a seat for releasably holding a pipette tip at their top tip opening. A displacement unit for air is integrated in the manual dosing device and, communicating by means of a channel, is connected to a hole in the seat. An air cushion is displaced by means of the displacement unit so that liquid is aspirated into, or discharged from, the bottom tip opening depending on the direction of displacement of the air cushion. The displacement unit is usually a cylinder having a plunger displaceable therein. The plunger is driven by means of a drive unit. Manual dosing devices that function with an air cushion are termed “pipettes”.
Direct displacement dosing devices work together with syringes. The syringes can be coupled to or released from the positive displacement dosing devices. The syringe cylinder is held in the positive displacement dosing device, and the syringe plunger is held in a seat body that can be displaced by means of a drive unit. By means of the drive unit, the syringe plunger is moved back and forth so that the liquid is aspirated into, or discharged from, an opening in the syringe.
Direct displacement devices that work together with small syringes with a similar size and shape as pipette tips are also termed “direct displacement pipettes”. Direct displacement dosing devices that work together with large syringes which are usually emptied in several steps are also termed “dispensers”.
Pipette tips and syringes are preferably made of plastic and can be thrown away after being used and replaced with new pipette tips or syringes.
Known manual dosing devices have a mechanical drive unit or electromechanical drive units. In addition, manual dosing devices having a manual drive unit with an electromechanical support (“servo drive unit”) are known. In addition, there are manual dosing devices with a fixed dosing volume, and manual dosing devices with an adjustable dosing volume. Furthermore, there are manual dosing devices with only one channel for use with only a single syringe or pipette tip, and manual dosing devices with a plurality of channels for the simultaneous use of a plurality of syringes or pipette tips. The invention relates to all of the above types of manual dosing devices.
Conventional manual dosing devices have a housing shaped as a handle made of a rigid plastic. These contain means for holding a syringe or pipette tip, a drive device, means for transmitting the drive movement of the drive device to a plunger or syringe, or a displacement unit for displacing an air cushion, operating elements and possibly display elements or other components. In the case of electrically-driven manual dosing devices, an electric drive motor, electronic control unit and batteries or rechargeable batteries are arranged in the housing. A plurality of components are therefore accommodated in a very small space in the housings of manual dosing devices. The housing simultaneously forms the support structure of the known manual dosing devices.
EP 2 033 712 A2, the entire contents of which is incorporated herein by reference, describes a dispenser that has a seat in a bottom end area of the housing for a syringe flange of a syringe. The syringe flange is held by means of syringe gripping levers that are mounted on pivot shafts in the bottom area of housing. Leaf springs are arranged on the inner jacket of the housing, and their top ends are fixed in the bottom area of the housing. The bottom ends of the leaf springs press against the inside of the syringe gripping levers to pretension them toward the position of gripping behind the syringe flange.
A spring-loaded thrust bearing is arranged in the seat against which the top side of the syringe flange can be pressed. The thrust bearing has sensors for scanning a code on the top side of the syringe flange.
A seat body with a plunger seat is arranged in the housing into which an upward projecting end section of a syringe plunger of the syringe can be inserted. Plunger gripping levers are mounted in the seat body that can grip behind a plunger collar on the outer end of the syringe plunger. The plunger gripping levers are pretensioned by legs springs toward a position in which they grip behind the plunger collar.
The seat body is driven by means of mechanical plunger positioning elements. These comprise a lifting unit connected to the seat body which extends out of the housing. Furthermore, the plunger positioning elements comprise a threaded spindle or rack that is also firmly attached to the seat body. An adjusting sleeve is seated on the threaded spindle, and its axial position is adjustable on the threaded spindle by means of an adjustment knob. Arranged in the top area of the housing is an actuating unit that has a pivoting actuating lever and can be actuated from the outside by means of an actuating button. A pawl is pivotably arranged on the actuating lever. The actuating lever is pressed upward by a spring, and the pawl is pretensioned by the spring toward the threaded spindle.
The actuating unit, the adjustment knob and the spindle are mounted in a plate-like holder with a laterally projecting bearing bracket that is inserted in the housing.
When a syringe is inserted in the syringe seat and held in the housing by means of the syringe gripping levers and the plunger gripping levers, the liquid can be drawn upward by moving the lifting unit. A dosing quantity is adjusted using the adjustment knob. By actuating the actuating unit, the syringe plunger is moved downward, and the desired amount of liquid is released. With each actuating stroke, the pawl falls into the threaded rod when it reaches the bottom end of the adjusting sleeve. The released dosing amount is set by adjusting the adjusting sleeve using the adjustment knob.
The actuating unit, the adjustment knob and the spindle can be premounted in the holder before it is inserted in the housing. Additional elements are not part of the holder or are mounted on it. In particular, the holder for the syringe flange is part of the housing. The spring-tensioned thrust bearing, the syringe gripping levers and the leaf springs are mounted in the housing. These means for holding the syringe must be mounted separately by the holder in the housing. The housing must therefore be very strong since drawing liquid into the syringe and ejecting liquid from the syringe exerts strong force on the means for holding the syringe. This restricts the selection of usable materials.
The disadvantage of known manual dosing devices is that the housing does not sit well in the hand, easily becomes dirty and is difficult to clean.
Against this background, the objective of the invention is to create a haptically improved manual dosing device.